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    CELOPLAST thread was designed at the beginning of the 1990s to be used in

    the assembly of plastic materials. CELOPLAST screws provide higher pull out

    resistance, improves ergonomics and avoid deformation of plastic bosses, greatly

    enhancing the technical properties of self-tapping screws. These advantages

    are obtained thanks to a combination of technical features specifi cally designed

    for fi xing plastic.

    CELOPLAST is recommended for assemblies with plastics with a bending modulus

    between 500 and 30.000 kg/cm2.

    ? 40o thread angle

    Changing the thread angle from 60o to 40o provides a 30% reduction in

    radial tension (FR) during the threading process, which avoids damaging the


    ? Increased thread height

    Rising the height of the thread gives 26% more penetration in plastic materials,

    improving pull out resistance.

    ? Increased thread pitch

    The volume of plastic material in the shearing zone (space between thread

    fl anks) is much bigger than with a self-tapping screw. In this way, we create

    a more resistant nut member, and consequently increase the failure torque


    ? Chamfered point

    Allows for a quick alignment of the screw.

    ? Less radial tension on plastic, allows for bosses with smaller diameter

    and reduces the problem of boss bursting.

    ? Quick alignment of screw before fi xing, thus reducing assembly time.

    ? Lower thread forming torque, which offers a more ergonomic assembly.

    ? More resistant to pull out and stripping, which enables its use in assemblies

    with high pull out resistance and/or compression requirements.

    ? The increase of surface contact between threads and nut member improves

    resistance to vibration loosening.

    ? Possibility to reuse the screw, reducing the risk of torque failure.

    All of these advantages directly translate into a more resistant assembly, greater

    safety during threading and lower costs in assembly process.

    Threading curve of CELOPLAST screw and self-tapping screw DIN 7891. Failure

    torque value is much higher with a CELOPLAST screw, giving safer assembly torque

    range (difference between thread forming torque and failure torque).

    4. CELOPLAST boss geometry.

    In order to assure a strong fi xing and guarantee the clamping of the assembly it

    is important to pay attention to the boss design, as this have to support mould

    extraction and cooling tension, as well as tension created during the insertion

    of the screw.

    The following table indicates the recommended dimensions for hole’s diameter

    and assembly depth in relation to the Bending Modulus of the plastic.


    REMFORM? thread was designed for plastic assemblies with high mechanical

    requirements. It’s recommended for assemblies with plastics with a bending

    modulus between 30.000 and 80.000 Kg/cm2.

    REMFORM? and REMFORM? ‘F’ are patented brands registered by CONTI FASTENERS AG and manufactured under

    licence by CELO.

    1. Technical features of REMFORM ? thread.

    ? Asymmetric thread

    This is the main feature of the REMFORM? thread. There are two noticeably

    different fl anks with respect to the perpendicular:

    - The steep trailing or pressure fl ank with a 12,5o angle minimizes radial

    force during threading process, thereby reducing the risk of boss bursting.

    Under tensile stress, it optimises pull out resistance.

    - The leading fl ank with a progressive angle creates asymmetrical radial

    stress during threading, improving material fl ow towards the pressure fl ank.

    The larger contact surface along the pressure fl ank of the screw increases

    resistance to stripping, vibrational loosening and pull out.

    ? Larger core diameter

    The increase in the core diameter with respect to conventional screws for

    plastic offers the possibility to work with higher assembly torques without

    breaking the screw. This helps to guarantee fi xing in deep assemblies with

    highly resistant plastics.

    ? Reduced thread diameter tolerance

    The reduction of the diameter tolerance provides greater uniformity in threading


    ? Less radial deformation on the plastic, reducing boss bursting problems

    and allowing for bosses with less external diameter.

    ? The narrow 12,5o angle of REMFORM? screw pressure fl ank provides very

    low thread forming torque values, therefore more ergonomic assembly.

    ? Strong pull out resistance of the assembly.

    ? The leading fl ank creates a larger surface contact between the screw and

    plastic material, increasing resistance to vibration loosening and stripping.

    ? Highly secure assembly. Low thread forming torque, together with high

    failure torque, results in a wide safe assembly torque range.

    ? Higher breaking torque value that allows for higher assembly torque and

    the possibility to work with deeper assemblies without increasing the diameter

    of the screw.

    All of these technical advantages results in a more resistant assembly, with a

    higher safe assembly torque range and savings on assembly costs.

    Black Zinc-Aluminium Flake Coating.

    ? 240h red rust resistance (resistance up to 720h on demand).

    ? Non-Electrolytic coating, there is no risk of hydrogen embrittlement.

    ? According European Environmental Regulations ELV and RoHS. Free of Cr (VI),

    Lead, Cadmium and Mercury.

    ? Conductive, non toxic and cathodic protection system.

    ? High mechanical and thermal resistance.

    Technical features of PLASTITE? 60 screw

    It is the fi rst version of the TRILOBULAR? screws for plastics. Currently it is not

    recommended as its performance has been improved with the CELOPLAST and

    REMFORM? screws.

    ? 60o thread angle.

    ? Thread pitch very similar to self-tapping screws.

    Advantages of PLASTITE? 60 screw compared to self-tapping screw

    ? Less radial deformation of plastic, reducing boss bursting problems.

    ? Once the screw is inserted, the fl ow of plastic between the lobes generates

    a high surface contact between the screw and nut member, increasing the

    vibration loosening resistance.

    ? The low friction generated during the threading process provides low threading

    torque, making the assembly more ergonomic.

    ? High pull out and stripping resistance.

    Technical data of PLASTITE? 60 screws

    Technical features of PLASTITE? 48-2 screw

    It is the fi rst improvement on the PLASTITE? 60 design, aimed at reducing stress

    on the plastic materials during the threading process. Maintains PLASTITE? features

    like TRILOBULAR? thread section and fl at crest lead thread on the

    screw tip.

    ? The 48° thread angle reduces radial tension during the threading process.

    ? The higher height of the thread allows for deeper penetration into the

    plastic, increasing clamping, pull out resistance and vibration loosening


    ? Twin lead thread. The steeper helix angle increases friction with the plastic

    material and, therefore, improves the failure torque value.

    Advantages of PLASTITE? 48-2 compared to PLASTITE? 60

    ? Less radial deformation of the plastic.

    ? Higher vibration loosening resistance.

    ? Increased pull out resistance and stripping torque.

    ? Increased productivity as the double thread provides faster assembly


    Technical data of PLASTITE? 48-2 screws

    Technical features of PLASTITE? 45 screw

    PLASTITE? 45 is the latest version of TRILOBULAR? screws for plastic.

    ? The 45o thread angle reduces stress caused during threading process, reducing

    radial tension and allowing a deeper penetration without increasing the

    thread forming torque.

    ? The larger thread pitch gives more tension relief over a larger plastic surface,

    resulting in an increased pull out and stripping resistance.

    To ensure the correct joint, it is very important to consider the boss design, as

    this have to support demoulding and cooling tension, resist the tension created

    during the insertion of the screw and guarantee the clamping of the assembly.

    The table below gives the recommended boss dimensions for hole diameters

    and assembly depths for the different PLASTITE? threads with different types of


    PCB screws have been designed to solve assembly problems with thin hard plastic

    parts and for the assembly on printed circuit boards (PCB).

    In the assembly of thin hard plastic parts with standard screws for plastic, the

    engagement length is not enough to avoid stripping and guarantee the pull out

    resistance of the assembly.

    Typical methods of assembly on PCB

    ? Inverted assembly. The assembly is done through the circuit and threading on

    the assembled part, for which a low assembly torque is necessary to avoid

    deformation of the printed circuit board. The head of the screw takes up a lot

    of space on the board.

    ? Welding.

    ? Use of plastic clips. The union can loosen in time due to the ageing of the

    plastic clips.

    The PCB screw has been developed to solve assembly problems with the aforementioned


    ? 40o thread angle

    The 40o thread angle reduces radial force FR generated during threading

    process, thereby avoiding bursting the plastic material and damaging

    the PCB.

    ? Special twin lead thread

    It provides greater surface contact with the base material, which increases

    friction and reduces stripping risk.

    ? Reinforced core

    The reinforced core allows for a higher assembly torque without breaking the

    screw and ensuring the resistance of the screw during assembly. This is essential

    when working with a hard base material.

    ? Pan head with stamped washer

    Increases surface friction in a way that also increases resistance to stripping.

    In the assembly on PCBs:

    ? The head of the screw is set directly on the connector, avoiding interference

    with the tracks.

    ? Direct fi xing without damaging the PCB.

    ? Higher resistance to vibrational loosening.

    ? Twin lead thread increases threading speed.

    3. Threading curve of PCB screw.

    PCB screw offers faster fi xing speeds due to the twin lead thread and safer assembly

    torque range: The failure torque is much higher with a PCB screw and

    the thread forming torque values are similar in both cases.

    4. PCB screw boss geometry.

    We recommend contacting our technical department for hole dimension and boss


    5. Applications of PCB screws.

    Assemblies on thin hard plastic.

    Assembly of components on printed circuit boards.

    This is a custom-made screw. For further information, please contact our sales


    IBI-ZAS thread has been designed to solve assembly problems with thermoset

    plastics. Due to the nature of these plastics, it is not recommended to use

    standard plastic screws, as the radial stress the base part is subjected to during

    thread forming can cause boss bursting.

    The features of this thread make it also a good choice when assembling aluminium

    and metal alloy parts with cone-shaped holes.

    1. Technical features of IBI-ZAS thread.

    ? Cutting thread

    The fi rst three lead threads of the screw have cuts that remove chips during

    threading process, decreasing the thread forming torque and the stress

    produced on the plastic material.

    ? Asymmetric thread

    Leading fl ank angle of 25o and trailing fl ank angle of 15o provides:

    - Increased pull out resistance.

    - Increased stripping resistance due to the harpoon effect of the threads.

    ? Reinforced core

    Ensures screw resistance during assembly, an essential requirement due to the

    extreme hardness of base material.

    ? Reduced thread pitch

    Increases contact points with base material, increasing resistance to vibration

    loosening and thread failure.

    2. Advantages of IBI-ZAS thread.

    ? Reduction of thread forming torque offering a more ergonomic assembly.

    ? Increased pull out and thread failure resistance, allowing for its use in

    assemblies with high pull out requirements.

    ? Improved breaking torque due to the screw’s reinforced core.

    ? Reduction in assembly costs:

    - The quality of the nut member allows the screw to be reused.

    - IBI-ZAS screw avoids the use of expensive metal inserts.

    ? The IBI-ZAS screw design avoids threading problems in cone-shaped holes

    (angle of mould extraction >4o) in aluminium and metal alloys.

    ? Twin lead thread

    The steeper angle increases the failure torque value and improves assembly


    ? Sharp points

    Allows for the insertion of the screw with no pilot hole.

    The table below gives the maximum width of the material to drill through in

    regards to the diameter of the TWINPLAST screw.

    ? Head with stamped washer

    Better distribution of tension on plastic material.

    2. Advantages of TWINPLAST screw.

    ? Allows for assembly on plastic parts with a minimum width of 1/3 the diameter

    of the screw.

    ? Prevents the design of bosses improving the plastic distribution during

    the blowing process.

    ? Reduction of thread forming torque, offering a more ergonomic assembly.

    ? Assembly with better pull out resistance.

    ? Higher stripping resistance, which prevents repairing during the assembly.

    ? The larger contact surface of the head allows for a better stress distribution

    on the plastic.

    ? Allows for reuse the screw, reducing the risk of stripping.

    3. Threading curve of TWINPLAST screw.

    Threading curve of TWINPLAST screw and self-tapping screw on PE blown part.

    TWINPLAST screw offers a safer assembly torque range, being forming

    torque lower and failure torque value much higher when compared to a selftapping


    The TRILOBULAR? PUSHTITE? thread was designed to be pressed into holes with

    a single, straight-line stoke, with the possibility to be removed without damaging

    the assembly.

    1. Technical features of PUSHTITE? II thread.

    ? TRILOBULAR? thread section

    Unlike screws with a circular section, the stress generated on the plastic during

    threading is concentrated on three points, reducing radial stress and thread

    forming torque.

    The space between the lobes permits air to escape during insertion.

    ? Asymmetric thread

    Leading fl ank of 70o for an easy entry of the screw.

    Trailing fl ank of 10o for a high pull out resistance.

    ? Helical harpoon thread

    It permits displaced air to escape during insertion and allows the screw to be

    removed and inserted if necessary.

    2. Advantages of PUSHTITE? II thread.

    ? Time and cost savings in assembly operations.

    ? The TRILOBULAR? thread section:

    - Minimizes the stress during insertion, avoiding the boss bursting.

    - Easies the air to escape, providing a quick and effi cient insertion.

    ? Prevents boss bursting by air occlusion.

    ? High pull out resistance.

    ? Allows reuse of the screw without boss damaging.

    It’s recommended for low mechanical requirements or Non-structural assemblies

    with DUCTILE plastics where is needed to reduce the assembly time.

    This is a custom-made screw. For more information, please contact our sales


    For the selection of a thread type, it is important to consider the type of plastic,

    the geometry of the parts to assemble and the different requirements of the


    The table below is a guide to select the thread to use based on the selection

    criteria listed, but fi eld tests will determine the best possible solution.

    CELO puts the application laboratory at your disposal, where suitable tests are conducted

    (threading, failure torque, pull out resistance, etc.) in order to recommend

    the type of thread that best meets the application requirements.

    TAPTITE II? TRILOBULAR? self-threading screws greatly reduce assembly

    costs and provide assemblies with high vibration loosening resistance.

    TAPTITE II? TRILOBULAR? screws are used to create a resistant and uniform

    thread into untapped holes during the fi xing process. Their use offers

    many advantages, both economically with an increase in productivity during

    assembly and by generally reducing costs, and technically, as they offer high

    mechanical performance during the assembly lifespan.

    CELO, S.A. produces the following screws with a TRILOBULAR? section:






    The stability in K value guarantees stable parameters while fi xing the screws. Only

    with the use of original screws can you ensure the stability of this parameter.

    ? The thread is formed by material lamination, without chips creation.

    The material displaced during threading, fl ows to fi ll the space between the

    lobes, completely wrapping around the shank of the screw and eliminating

    the tolerance between screw and thread in the nut member.

    ? TRILOBULAR? TAPTITE II? screws form threads into untapped nut member

    with the tolerance of a machine thread. In this way it is possible to replace

    TAPTITE? screw with a standard machine screw.

    ? The manufacturing process for the TRILOBULAR? screws normally includes case

    hardening, quenching and tempering heat treatment with the objective of

    reaching a surface hardness of at least 200 HV higher than the base material.

    The heat treatment applied can be modifi ed according to the application and

    particular screw requirements.

    The surface and core hardness values are detailed later on for the different thread


    The detailed features and associated advantages can only be achieved with TRILOBULAR

    ? TAPTITE II? screws manufactured according to the manufacturing

    standards of the REMINC company.

    ? Low threading torque allowing for a more ergonomic assembly.

    ? High values of prevailing torque ensuring excellent vibration loosening


    ? Forming thread by lamination avoids chips creation, which is important for

    electronic applications and ensures a high pull out resistance.

    ? High failure torque value.

    ? The progressive point allows for:

    - Easy insertion into the hole.

    - Minimum force to start thread forming.

    - An ideal solution for automatic assembly.

    TRILOBULAR? TAPTITE II? threaded screws eliminate problems of:

    ? Misalignment of machine screws in tapped holes, avoiding the use of guiding

    components (screws with dog point…).

    ? Screw loosening by vibrations.

    - Avoid the use of blocking elements (lock washers, adhesives patches, etc.).

    - Eliminates retightening (which does not prevent vibration loosening).

    The TRILOBULAR? screws admit more variations in hole sizes than machine screws

    in tapped holes.

    Only 15% of all assembly costs corresponds to the cost of the screw. The

    TRILOBULAR? TAPTITE II? thread screws have been specially designed to

    reduce the remaining 85%.

    The TRILOBULAR? TAPTITE II? screws eliminate separate tapping operations

    and associated costs:

    ? Direct or indirect labour cost.

    ? Threading lubricants.

    ? Preparation.

    ? Cleaning of oils and chips.

    ? Inspection, loss or repair.

    TAPTITE II? screw is the most popular in the TRILOBULAR? family of self-threading

    screws. TAPTITE II? screws create a high performance nut into drilled, punched

    or extruded holes in steel and light alloys.

    1. Technical features of TAPTITE II? screw.

    ? TRILOBULAR? thread section.

    ? 60o thread angle and machine thread pitch.

    ? Progressive point that reduces threading torque. TAPTITE II? thread has 2-3

    thread leads that improve screw insertion and threading of the screw.

    ? Machine thread confi guration. The nut created in the base material has the

    standard machine thread tolerance.

    ? Case hardening, quenching and tempering heat treatment in agreement

    with TAPTITE? manufacturing standards. Depending on the requirements of

    the screw, alternative heat treatments can be applied.

    ? In the last stage of the manufacturing process, a special lubricant is applied

    to make thread forming easier.

    Due to the hardness of the screw, with electrolytic coatings it is necessary to apply

    baking treatment to avoid hydrogen embrittlement (page 102).

    ? Low threading torque, even in deep holes, ensuring ergonomic assembly.

    ? Axial alignment of screw.

    ? High Failure Torque Resistance.

    ? High Pull out Resistance.

    ? High Prevailing Torque, which exceeds the level offered by machine screws

    with locking nuts.

    ? Excellent vibration loosening resistance, eliminating the need for complementary

    assembly systems.

    ? The nut created is compatible with machine screws.

    Cost saving and improvement of mechanical properties for:

    ? Assemblies on steel parts with drilled, punched or extruded holes.

    ? Assemblies subjected to vibrations and severe temperatures.

    ? Assemblies with free of chips contamination requirement.


    Automotive components (rear-view mirrors, power steering systems, windscreen


    Electric material.


    Household appliances.


    TAPTITE 2000? screws offer all the benefi ts of TAPTITE II? screws with the

    addition of Radius Profi le? thread and improved TRILOBULAR? thread,

    which improves the thread forming process and strengthens the assembly,

    increasing the vibration loosening resistance.

    TAPTITE 2000? thread screws provide many opportunities to reduce assembly

    costs and provide excellent mechanical properties.

    ? Reduced TRILOBULAR? thread

    TAPTITE 2000? thread section is less TRILOBULAR? than the TAPTITE II?,

    creating more surface contact between the screw and the nut member.

    Double TRILOBULAR? thread design for M6 and larger screws:

    The thread leads (Section B-B) have generous lobulation, which reduces friction

    during thread forming, guaranteeing a more ergonomic assembly.

    The shank of the screw (Section A-A) has moderate lobulation, which increases

    surface contact between the screw and nut member, improving pull out and

    vibration loosening resistance.

    ? Radius Profi le? of the thread

    Ensures the maximum surface contact between the screw and nut member,

    offering higher vibration resistance.

    ? Progressive point that reduces initial threading torque

    The thread leads enhance the screw insertion and thread forming.

    ? Machine thread confi guration

    Double TRILOBULAR? thread for M6 and larger:

    ? Reduces thread forming torque, providing a more ergonomic assembly. For

    the same diameter, the thread forming torque of the TAPTITE 2000? is 10%*

    less than the TAPTITE II?.

    ? Improves pull out resistance.

    The Radius Profi le? provides:

    ? High prevailing torque.

    ? Excellent vibration loosening resistance.

    ? Higher thread failure torque.

    ? High assembly torque, transmitting higher clamping to the assembly.

    ? Safer assembly torque range, reduced thread forming torque and increased

    thread failure value.

    ? Optimum load bearing capacity.

    ? Perfect Axial Alignment:

    - Easy insertion.

    - The screw remains perpendicular with respect to the plane of the hole.

    - Minimum effort to start thread forming.

    - Ideal for automatic assembly.

    3. Comparison between TAPTITE 2000? and TAPTITE II ? screws.

    Tests done with TAPTITE 2000? and TAPTITE II? screws, M8x1.25.

    Thread forming torque

    4. Recommended hole diameter for TAPTITE 2000?.

    See the information given in the TAPTITE II? screws section.

    5. Applications of TAPTITE 2000? screws.

    TAPTITE 2000? screws have been specially designed for assemblies in steel and

    light alloys:

    ? Components that require a low threading torque.

    ? Structural components that need a high pull out resistance.

    ? Components that require a high tightness level.


    Water pumps.

    Motor assembly.

    Assembly of washing machine components.


    CORFLEX? N heat treatment provides higher durability to TAPTITE 2000? screws,

    improving bending and heavy load cycles resistance. It has been specially designed

    for high demanding requirements assemblies in aluminium and light alloy



    ? Excellent resistance to shock and alternating loads.

    ? Ability to thread in large sections.

    ? Can be adapted to specifi c hardness or toughness requirements.


    CORFLEX? N treated screws can only be used in applications with ALUMINIUM


    CORFLEX? N is recommended for applications exposed to:

    ? Shear stress.

    ? Corrosion.

    ? Vibrations.

    ? Alternating loads.

    ? Severe temperature cycles.

    All CELO products with TRILOBULAR? threads can be treated with CORFLEX? N

    upon request.

    NT85T family product combines the features of TAPTITE? 2000 with

    CORFLEX? N heat treatment.

    TAPTITE? ‘CA’ screw is based mainly on the TAPTITE II? or TAPTITE 2000?

    design, depending on the customer request.

    TAPTITE? ‘CA’ screw has a gimlet point for use in assemblies where the clearance

    and pilot holes are not aligned.

    1. Technical features of TAPTITE? ‘CA’ screw.

    ? TRILOBULAR? thread section. This can be TAPTITE II? or TAPTITE 2000?


    ? Sharp point especially designed to:

    - The alignment of the screw, in applications where the holes are not aligned

    and rapid hole fi nding is essential.

    - Allow the progressive insertion of the screw, lowering the initial threading


    ? The CA point is also good for diffi cult access applications.

    ? The CA point can be fi tted with a sharp tip (known as the Cut off point) or with

    a blunt tip (Non-cut off point).

    The Cut off point is recommended for applications in which it is necessary to

    pierce into the material without making a pilot hole.

    TAPTITE? ‘CA’ screws are recommended for:

    ? Assemblies where the clearance and pilot holes are not aligned.

    ? Diffi cult access applications and deep holes.

    ? Assemblies were it is required to pierce material without of making a pilot hole

    (TAPTITE? ‘CA’ Cut off point).

    This is custom-made product. Please, contact our sales department for further


    The TRILOBULAR? POWERLOK? thread was designed to provide solutions

    to loosening problems in tapped holes, especially in applications exposed to

    severe vibrations or cycles of expansion/contraction.

    POWERLOK? is the only screw with the locking concept: the thread design provides

    locking ability along the length of the thread, independently of the base

    material and of the temperatures reached during assembly life.

    This is not a self-threading screw, it needs tapped holes.

    ? Combination of 60o- 30o thread form. The penetration of the POWERLOK?

    lobes in the nut member allows the 30o thread crest on the thread to fl ex elastically

    under clamp load, simulating the live action of spring washers.

    ? TRILOBULAR? thread section.

    ? Slight increase in the thread major diameter. The tolerances are slightly higher

    over equivalent size machine screw, which increases stripping resistance of the


    ? Case hardened and tempered in accordance with POWERLOK? manufacturing


    ? POWERLOK? screws are lubrifi ed to make easier the fi xing process.

    ? Due to the hardness of the screw, it is necessary to apply baking treatment to

    avoid hydrogen embrittlement (page 102).

    To ensure correct performance of the screw, it should have higher hardness value

    than the nut member. We recommend consulting our technical department for

    the viability of POWERLOK? screws for each particular application.

    ? Immediate and continuous locking action. It allows for repeated insertions

    and removals without affecting its locking ability and independently of nut


    ? The spring effect of the 30o thread crest maintains clamping.

    ? Excellent vibration resistance, eliminating loosening problems in tapped

    holes and nuts without the use of additional locking elements (lock nuts, spring

    washers, adhesive patches,…).

    ? Cost reduction by eliminating the need for additional locking elements

    Assembly of components under severe vibration conditions or cycles of expansion

    / contraction in tapped holes.

    Cost reduction and better performance with the elimination of adhesive patches

    for metric screws and locking nuts.


    Assembly of automotive components (rear-view mirrors, etc.).

    Assembly in washing machines, motors,…

    Thin metal sheet is understood as having a thickness of less 1/3 the nominal

    diameter of the screw.

    FASTITE? 2000? screws have been specially developed for the assembly

    on thin metal sheets, guaranteeing joint clamping with a minimum risk of

    assembly failure, while offering excellent pull out and vibration loosening


    FASTITE? 2000? offers a profitable and efficient assembly due to the

    TRILOBULAR? thread, with better resistance to breaking torque and torque failure

    compared with other screws.

    ? Radius Profi le? of standard TAPTITE 2000? increases contact surface

    between the screw and nut member.

    ? Twin Lead Thread, which allows for a quick and effi cient fi xing process.

    ? Fully threaded shank to avoid clipping when screwing in thin metal sheets.

    ? Hollow ring under screw head to absorb the metal sheet deformation and

    allow for a perfect seal between screw head and sheet.

    ? The serrations under the screw head increases the failure torque and vibration

    loosening resistance.

    ? The special extruding point increases the assembly engagement length

    during screw insertion.

    ? The Cut off point (optional) permits piercing in sheets with no prepared

    hole without deforming the sheet. We have the PG Screw with cut off point

    available in stock.

    2. Advantages of FASTITE? 2000? screw.

    ? The TRILOBULAR? thread section offers low threading torque.

    ? The Radius Profi le? and the extrusion created in the metal sheet provide high

    pull out and vibration loosening resistance.

    ? The Twin Lead Thread screw increases the torque failure by approx. 50%

    in comparison with a simple thread screw.

    ? High prevailing torque.

    ? High clamping of the assembly.

    ? Excellent alignment of screw in the hole, keeping the screw vertical from

    the start of the screwing process until the end.

    ? Profi table and effi cient fi xing in comparison with other types of screws and

    assembly solutions.

    3. Threading curve of FASTITE? 2000? screw.

    The following graph shows a comparison between DIN 7981 screw and

    FASTITE? 2000? screw on Aluminium sheet of 1,4 mm thickness.

    Assembly with FASTITE? 2000? screws offers a higher assembly torque range

    safety margin as well as a faster fi xing process. The double thread and longer

    assembly length provide a higher failure torque value.

    4. Recommended hole diameter for aluminium and steel sheets.

    The following table shows the recommended hole diameter for different thicknesses

    of aluminium and steel sheets in relation to the nominal diameter of the

    screw. Hardness of the steel sheets tested: 125-150 HV.

    TAPTITE II? screws offer many advantages for fi xing metals but do not guarantee

    a perfect assembly when metal sheet thickness is less than 1/3 the screw’s nominal

    diameter. The reduction of the surface contact between the thread and the nut

    member is not enough for high pull out resistance requirements when working

    with thin metal sheets.

    TRILOBULAR? EXTRUDE-TITE? screws have been designed to solve problems of

    pull out resistance and torque failure in assemblies with thin metal sheets, which

    require a machine screw.

    EXTRUDE-TITE? screws meet grounding connection standards, therefore they are

    ideal for applications that require electrical conductivity.

    Reduced TRILOBULAR? section guarantees more surface contact with the nut

    member and increases pull out resistance.

    Non-cut off point style for quick and effective penetration, ensuring the alignment

    of screw in the hole.

    2. Advantages of EXTRUDE-TITE? screw.

    ? Low thread forming torque guarantees an ergonomic fi xing process.

    ? High vibration loosening resistance.

    ? High pull out strength.

    ? Axial alignment of the assembly components, allowing for use in off-centred


    ? Possibility of piercing thin materials with the optional cut off point.

    ? Cost savings as it:

    - Allows for the assembly of thinner and lighter materials.

    - Eliminates need for repairs due to thread failure and off-centred screws.

    3. Recommended hole diameter for aluminium and steel sheets.

    See the information on FASTITE? 2000? screws.

    EXTRUDE-TITE? screws are recommended for assemblies on thin metal sheets

    that require a screw with high mechanical performance and machine thread

    confi guration.


    Grounding connections for household appliances.

    Assembly of household appliances.

    This is custom-made screw. For further information, please, ask our sales department.

    To correctly use self-tapping screws, the thickness of the sheet must be equal

    to or larger than the pitch of the screw.

    Self-tapping screws have been widely used for fi xing thin metal sheets. They are still

    being used, although there are more appropriate solutions like FASTITE? 2000?

    and EXTRUDE TITE? screws.

    If we try to use self-tapping screws in assemblies that do not meet the thickness

    requirement mentioned above, the following problems occur:

    ? Torque failure.

    The reduced safety margin between the thread forming torque and torque failure

    means that a slight out-of-adjustment in the screwdriver’s calibration could cause

    torque failure.

    Small variations in the dimensions of the screw and/or hole diameter cause torque

    failure in a large number of screws with the correct value of assembly torque.

    ? Low pull out and vibration loosening resistance.

    On many occasions, the unthreaded part of the screw under the head is larger

    than the thickness of the assembly, causing the screw to clip the sheet.

    ? Reduced clamping of the assembly.

    The assembly torque is set to minimum to avoid torque failure problems, which

    provide low clamping of the assembly.

    ? Diffi cult axial alignment.

    In most cases, the thread design causes misalignment of the screw.

    Printed circuit boards (PCBs) have a series of components assembled using

    different systems, depending on its functionality and existing technologies.

    Typical methods of assembly on PCB.

    ? Inverted assembly. The assembly is done through the circuit and threading on

    the assembled part, for which a low assembly torque is necessary to avoid

    deformation of the printed circuit board. The head of the screw takes up a lot

    of space on the board.

    ? Use of machine screws for the assembly of the heat sink with tapped holes.

    ? Welding solution.

    ? Use of plastic clips. The union can loosen in time due to the ageing of the

    plastic clips.

    ? Use of metric screws for the assembly of heat sinks with threaded holes.

    There are different alternatives to the aforementioned assemblies that offer large

    assembly cost savings.

    Below are detailed solutions for different types of assemblies on PCB circuits

    1. Assembly of PCBs on aluminium pieces.

    Depending on the geometry of the aluminium heat sink, it is possible to use either

    TAPTITE II? or REMFORM? ‘F’ screws.

    Aluminium heat sinks and frames with drilled holes.

    In these cases it is recommend to use TAPTITE II? screws. The advantages compared

    with the traditional assembly method with machine screws include:

    ? Cost reduction as there is no need for previously tapped holes.

    ? Thread forming by lamination, preventing chips creation.

    ? Loosening resistance caused by the thermal gradients that take place within

    the heat sink.

    ? Elimination of cross threading problem.

    For further information, please consult the TAPTITE II? description on page 46.

    The reference TT22T, TAPTITE II? thread, incorporates a fl exible washer offering

    the following advantages:

    ? Ensures a consistent clamping of the assembly throughout the product’s

    life span.

    ? Increases vibration loosening and thermal gradient resistance.

    ? Easy assembly in hard-to-reach positions.

    ? The washer rotates freely, preventing damage on the board during assembly.

    Extruded aluminium heat sinks with open holes.

    In these cases, it is recommend to use REMFORM? ’F’ screws. The advantages

    compared with the traditional assembly method with machine screws are:

    ? Cost reduction, as there is no need for previously tapped holes.

    ? Threading without chips creation.

    ? Loosening resistance caused by the thermal gradients that take place within

    the heat sink.

    For further information, please consult the REMFORM? ‘F’ description on

    page 21.

    2. Assembly of connectors on the PCB.

    For assembling connectors on the PCB, we recommend using PCB screws (page

    29) threaded directly onto the PCB.

    Advantages using PCB screw vs. conventional assembly systems.

    ? The screw head sits directly on top of the connector, preventing interference

    with the paths and providing a more effi cient use of available space.

    ? Direct threading without damaging the PCB.

    ? Prevents vibration loosening.

    ? Faster threading.

    This is a custom-made screw. For more information, please contact our sales


    3. Fixing of PCB to metal chassis or assembly of electrical connections.

    The fi xing of a PCB to a metallic frame or the assembly of electrical connections

    is done with a machine screw-nut system.

    In most cases, SEM screws are used to prevent vibration loosening and make the

    installation easier. The screw incorporates a grower washer to ensure clamping

    and a fl at washer to distribute load across the entire surface and prevent damage

    on the piece from punctual contact with the grower washer.

    CELO offers the pan head Torx? recess M22T screw with one cone-shaped washer

    that replaces the aforementioned two washers, ensuring clamping over the surface

    under the washer and preventing damage on the piece by punctual contact.

    This is a custom-made screw. For more information, please contact our sales


    There are many industrial applications where it is necessary to ensure that the

    product is sealed to avoid any outside tampering by unauthorised personnel. We

    can fi nd different sealing systems on the market, one of the most widely used

    solution is mechanical manufactured sealing screws. This solution has limitations

    with regard to thread and recess design, as well as materials used.

    For this reason CELO propose the use of the SEALING screw made with stamping


    1. Technical features of SEALING screws.

    ? Head type

    - Small or large cylindrical head.

    - Possibility to make one or two holes.

    ? Recess type

    - The stamping manufacturing process makes possible the combined recess

    POZI + SLOT.

    - In cases where the height of the head does not allow for a POZI recess, as it

    would interfere with the hole, a Slot recess can be used.

    ? Thread type

    - The stamping manufacturing process makes it possible for self-threading

    screws for plastics (CELOPLAST, REMFORM?, REMFORM? ’F’), so no metal

    inserts are needed.

    - Machine and partial thread.

    2. Advantages of SEALING screws.

    ? Screws made of steel allowing for cost reduction. Normally mechanical

    manufactured sealing screws are made of nickel-plated brass.

    ? Screws made of steel offer better mechanical properties.

    ? The POZI + SLOT recess improves the assembly process on automatic assembly

    lines and makes the SLOT accessible for the installer.

    ? The plastic thread eliminates the need for metal inserts, offering:

    - Cost reduction for both the price of the insert and its insertion in the


    - Easily recycled parts. It is not necessary to separate the insert from the

    plastic to recycle the piece.

    - Increased vibration loosening resistance (for more information, see


    The screws used in grounding assemblies have to meet the requirements indicated

    in regulation EN 60335-1:2002, with the aim of offering a correct assembly and

    guaranteeing electrical conductivity.

    Some of the existing possibilities for grounding assemblies are:

    ? Machine thread screw + washer + nut. Disadvantages: problems with automation,

    high component cost and vibrational loosening problems.

    ? TAPTITE II?. Disadvantages: problems with pull out and torque failure resistance

    in thin metal sheets.

    For grounding assembly we recommend the TRILOBULAR? EXTRUDE-TITE?

    screw (see description on page 70), with the inclusion of pointed serrations on

    the underside of the head to ensure electrical conductivity.

    The TRILOBULAR? EXTRUDE-TITE? screw meets all established standards in

    regulation EN 60335-1:2002, which are listed below:

    ? The screw should be tightened and loosened 5 times maintaining its initial

    properties and required clamping level.

    ? This test is conducted with the correct tool and using the assembly torque

    indicated on the table.

    2. Advantages of EXTRUDE-TITE? screw

    ? Ergonomic threading process.

    ? High vibration loosening resistance.

    ? Increase of pull out resistance.

    ? Axial alignment of assembly components, allowing for its use in off-centre


    ? Rapid screw assembly.

    ? Allows for automatic assembly and reduction of references, with a subsequent

    cost savings in the assembly process.

    The double end studs is used to easily assemble two parts. One of the threads

    stays set in the fi rst part, allowing the assembly of the second part with a nut.

    1. Technical features of DOUBLE END STUDS.

    Double end stud combines two threads along both sides of its shaft, which may

    be the same thread type or different depending on the materials and the fi nal

    requirements of the assembly:

    1st part: Machine Thread + External TORX? recess.

    These screws are characterised by having a machine thread as a screw head. It

    normally has an external TORX? recess to facilitate automatic assembly. It is also

    possible to use the intermediate hex washer to transmit the threading torque.

    2nd part:

    On the second part of the screw, different types of threads, depending on the

    need, can be used:

    ? REMFORM?, REMFORM? ‘F’, CELOPLAST or PLASTITE? Thread if assembly

    is being done on plastic parts.

    ? TAPTITE II? or TAPTITE 2000? Thread if assembly is done on light alloy parts

    (Zamak, Aluminium,…).

    ? MACHINE Thread if the assembly is being done with metal parts with threaded

    holes or with a nut.

    The double end stud enhances the assembly of two parts as it has two sets of

    threads on one part.

    First you set the self-threading part of the screw (part 2) in the piece, leaving the

    machine thread (part 1) waiting to be mounted later to the fi nal support.

    In most applications using double end studs, the fi nal assembly is done in automatic

    assembly line, therefore it is recommended to incorporate the Optical

    Sorting system to the manufacturing process (see page 105).

    Fuse holders incorporate a screw with specifi c features which makes assembly

    easier and assure the cable tightening.

    Terminal screws are produced according to specifi c requirements of each

    customer and application, but keep some general features that are detailed


    Features of TERMINAL screws

    ? Cylindrical head. Normally terminal screws are placed inside reduced space in

    the fuse holder, therefore small diameter head is required.

    ? Combined recess. Terminal screws are produced with the combined recess

    POZI + SLOT, PHILIPS + SLOT, or TORX? + SLOT which improves the assembly

    process on automatic assembly lines and makes the SLOT accessible for the


    ? Machine thread type.

    ? Flat point. To assure cable tightening, it’s absolutely necessary to get a complete

    fl at point and free of burrs to avoid cable damaging.

    ? If required, the screws can be produced quality 8.8.

    Depending of the fuse holder type there are other alternatives for the terminal

    screw design. In applications where is required to tighten the cable with a washer,

    it’s possible to produce the terminal screw with captive washer.

    The washer and its assembly fulfi l the specifi c requirements to assure the correct

    cable tightening.

    It is recommended to follow ISO/DIN standards for each type of screw. The ISO/DIN details the head dimensions for

    different types of recesses and threads and their quality requirements.

    These recommendations can be modifi ed in accordance with the needs of each use, reducing head height or increasing

    diameter. In these cases, the feasibility of the heading process should be considered.

    In many cases, an oversized screw head, compared to the thread diameter, is necessary. This may be due to a large

    washer or a big head to avoid breaking during assembly. In these cases, it is important to analyse the feasibility of the

    heading process, which in many cases is a 3 or 4 blows.

    The recess is one of the main elements of a screw and is usually a notch or socket in the head, although there is another

    series of indented or concaved recesses that transmit the rotation of the screwdriver to the screw.

    The recess is the junction point between the fastening system and screw. It’s responsible for transmitting

    the rotation of the screwdriver to the screw. The turning force is measured by a scale known as

    torque and the recess absorbs the torque and transmits it to the screw.

    There are many parameters that define the performance of a recess. The following defines the most important

    factors to consider:

    - Torque transmission: is the most important recess feature. The less effort lost at the

    transition-point in the recess, the better the torque transmission. A high torque transmission

    allows us to save energy in the tightening process and avoid problems of rounding and

    damaging the recess and the driver bit.

    - Camout: is the force on the walls of the recess generated by torque transmission. Camout

    greatly reduces torque transmission and make assembly diffi cult.

    - Alignment: is a property that some recesses have to help guiding the screw along the axis of

    rotation in order to ease its position into the hole, so that we can apply the proper preload on the

    self-threading or self-tapping screw without slipping out.

    - Engagement speed: Is the speed in which the bit of the screwdriver finds the recess and can start to transmit

    torque. Typically, the less you have to turn the bit to enter the recess, the higher the engagement speed. For

    this reason, six-lobed symmetrical recesses have a faster engagement speed than cross-shaped ones (with

    only four lobes).

    - Ageing: screwdriver bits are damaged over time. Friction or heavy workloads are some of the factors that weaken

    the bit. It is important to choose a recess that minimises the wear on bits due to their high cost. It is likewise important

    to ensure that the bit-recess system is used correctly.

    - Stick fi t: is the ability of some bit-recess systems to connect without a magnetic bit holder. This ability is due to the

    friction created by the shape of the bit and the inner walls of the recess. This feature is very valuable in operations

    with low accessibility, and it is generally not used in automatic assembly lines.

    - Tamper-proof: Tamper-proof recesses require specifi c bits to allow for adequate torque transmission.

    - One-way: One-way recesses do not allow for removal once the screw is in place.

    Companies have patented many of the existing recesses, and other recesses follow standards defi ned by relevant

    international organisations. The best-known standardised recesses are PHILIPS and Six Lobular recesses, but there are

    other widely used original patented designs that offer an improved tip-recess system. It is important to remember that

    the correct engagement is achieved by using the appropriate bit for each recess. Licensed recesses undoubtedly make

    up an essential part of the system if we do not want to reduce the crimping properties between them.

    A small variation in tolerance, inner wall angle and depth of the recess can increase the wear on bits and cause ergonomic


    The following international standards defi ne recesses:

    DIN EN ISO 10664

    DIN EN ISO 4757

    The most common patented ones are:






    Diagonal cut in the screw head that is deep enough to transmit the required

    torque for threading the part.


    ? Popular.

    ? Easy to clean off any possible paint residue.


    ? Being an open recess, the screwdriver bit slips easily. Therefore it cannot be

    used reliably in either automatic assembly or with electric or semi-automatic

    pneumatic tools.

    ? Low torque transmission.

    ? Low engagement speed, as the bits needs to turn 90o to engage.

    Using a combination of recesses can solve these problems.

    Main applications.

    Slot screws are commonly used in the electric sector.


    Cruciform and cone-shaped recess. The PHILIPS recess can be combined with a

    slot or hex head.


    ? Popular.

    ? Compatible with automatic assembly.


    ? Camout effect. Due to the conical shape of the internal walls, the screwdriver

    bits have the tendency to slip from the recess. To compensate the camout

    effect, more axial load needs to be applied.

    ? The diffi culty in bit engagement lowers the torque transmission.

    ? The force required to compensate the camout effect reduces driver bit life.

    Main applications.

    It is present in all sectors: automotive, metallic carpentry, toys, electric material,

    etc… Normally, self-tapping screws have this recess.


    Cruciform recess developed to improve the performance of the PHILIPS recess.

    The internal walls are less cone-shaped, reducing the camout effect. They are

    visually distinguishable from PHILIPS due to the four small points between the

    arms. It can be combined with the slot or hex head.


    ? Popular.

    ? Improved torque transmission compared to PHILIPS recess.


    ? Although performance has improved in comparison to the PHILIPS recess, the

    aforementioned cam-out effect still occurs.

    Main applications.

    It is mainly used for wood screws, self-tapping screws for plastic and TAPTITE II?



    This is a POZI or PHILLIPS recess combined with a slot. It is made by stamping,

    which greatly reduces costs compared with the slot recess.


    ? Allows for the use of POZI or PHILLIPS tips on assembly lines, leaving the SLOT

    for the installer.

    Main applications.

    Mainly used in the electric sector.


    ? The 60o angle of incidence makes diffi cult the torque transmission.

    ? The screwdriver bit sporadically contacts the edges of the recess, resulting in

    recess damaging and the creation of tension in the head of the screw.

    ? To ensure effi cient torque transmission, high recess depth and high head height

    is necessary.

    ? Not recommended for automatic assembly lines.

    Main applications.

    It is recommended for high-resistance screws requiring high-assembly torque

    (class 12.9, 10.9, etc.), headless screws and DYI parts.


    The vertical walls eliminate the camout effect, increasing driver bit life and allowing

    more ergonomic threading.

    The 15o angle of incidence greatly reduces the radial stress, increasing tool bit life

    and improving torque transmission.

    The six lobes allow for faster engagement speed.


    ? Its great strength and resistance to recess damaging (with no possible camout

    effect) make it an excellent choice for uses that require high-assembly torque.

    ? The six lobes allow faster tool engagement, which makes it one of the best

    tip-recess systems for automatic and robotic processes.


    ? The tolerance between the driver bit and the recess makes it very diffi cult to

    use with high speed drilling systems.

    ? It’s not recommended for self-drilling screws.

    ? To ensure effective transmission, there needs to be a deeply cut notch.

    Recess sizes.

    The size of the recess varies with the diameter of the screw and it can be modifi ed

    to the requirements of each use.

    This is an improvement on the TORX? recess. TORX PLUS? elliptically

    based geometry provides greater contact area between the screwdriver

    bit and screw recess, maximizing engagement of driver bit and recess

    and allowing for high assembly torque even at higher revolutions.

    The vertical walls eliminate camout effect and offer perfect tool engagement,

    thereby reducing the risk of tool slippage and minimizing

    damage it can cause.

    The 0o angle of incidence eliminates the radial stress produced at

    the point-to-point contact, increases driver bit life and ensures optimal

    assembly torque transmission.

    ? Faster tool engagement.

    The design features and uses for the TORX PLUS?, recess make it one of the

    best recess systems for automatic and robotic systems.

    ? TORX PLUS? Drive recess completely encloses the driver tip, preventing tool

    slippage and damage to the surrounding surfaces.

    ? Screws with TORX PLUS? recesses can be used with TORX? drive bits.


    ? It is not recommended for assembly with self-drilling screws.

    ? Like the TORX? recess, it requires a deeply cut notch.

    Recess sizes.

    The sizes of recesses vary on the diameter of the screw:

    4 IP, 5 IP, 6 IP, 7 IP, 8 IP, 10 IP, 15 IP, 20 IP, 25 IP, 30 IP.

    Selection of the recess size can be modifi ed according to the requirements of

    each use.


    The external TORX PLUS? recess was developed for use with low height

    heads, which could not house a TORX PLUS? recess and for its use in Double

    End Studs.


    Six lobes recess specially designed for portable electric tools. It is manufactured

    under license by AW? (Adolf Würth GmbH).


    ? The vertical walls eliminate the camout effect, which provides optimal assembly

    torque transmission and less battery consumption.

    ? Internal conical shape of the lobe grants a perfect fi tting in the recess, reducing

    bit damage.

    ? The SIT? recess is compatible with TORX? screwdriver bits, although a perfect

    fi t is only possible with original SIT? driver bits.

    Tamper-proof recesses were developed to avoid any tampering of the screw after

    assembly. The manufacturer controls the distribution of the driver bits; therefore

    it is used only by authorised personnel.

    TORX? Tamper-proof


    The TORX? Tamper-proof recess was developed to allow manufacturers to use the

    TORX? recess and, thanks to the controlled distribution of the driver bits, guarantee

    that end users cannot manipulate the screw. The recess has a solid post formed

    in the centre of the recess, blocking the use of a standard TORX? bit.


    ? The post can be removed and a standard TORX? bit can be used to remove the screw.


    TORX PLUS? Tamper-proof recess has fi ve lobes and a solid post formed in the

    centre of the recess.


    The screw is extremely diffi cult to remove without a special tamper-resistant

    TORX PLUS? Drive tool.



    This is not a common recess. It is available in fi ve sizes: #0, #1, #2, #3 y #4. It’s

    patented by PHILIPS SCREW COMPANY.


    The special TRILOBULAR? shape of the CELOK? recess ensures a high tamperproof

    level as there is no conventional tool fi tting in the recess. The distance

    between two opposite points is constant along the diameter perimeter, making

    impossible for any conventional screwdriver to be used on it.


    ? Good torque transmission.

    ? CELO,S.A. sells special CELOK? screwdriver bits only to customers who buy

    CELOK? screws.

    ? It has Stick-fi t effect.


    Screws and other fixing elements made of steel and its alloys should have a coating to protect them against

    corrosion and improve aesthetics. The corrosion resistance is indicated in HSS (Hours Salt Spray).

    There are many different coatings which corrosion resistance depends not only on the coating type itself but

    also on the reliability of the process applied. There are many available tests to evaluate their quality: thickness

    layer, climatic test, adherence test,… These are complementary tests and should be applied and used correctly

    to avoid wrong conclusions. In all cases, we recommend to follow the international standards.

    Layer Thickness

    There are many methods to determine the layer thickness. It will depend basically on the base material, coating

    applied, piece geometry,… For screws and other fixing ferrous elements with complicated geometry (small flat

    surface), the X-rays measurement system is the most widely used for its rate and reliability. In this case, the

    coating layer must be homogeneous, e.g. Zinc, Nickel and copper electrolytic coatings.

    ISO 4042 standard describes the optimal thickness measurement point and the maximum values recommended

    according to the screw pitch and thread diameter.

    It’s commonly thought that the higher the thickness, the better the corrosion resistance. This is not fully correct,

    as its efficiency depends on other factors like adherence, passivated quality and sealant presence. These

    parameters can’t be evaluated by any thickness measurement technique and should be complemented by the

    following tests:

    Salt Spray Chamber

    Salt Spray Chamber (SSC) is a climatic test that tries to simulate the worst environmental conditions for a

    ferrous material, like the marine environment. This test allows for a total quality evaluation of the coating,

    but its long testing time (from 3 to 20 days depending on the coating) makes it not suitable for the daily

    quality control.

    There are many reference standards like DIN 50.021, ISO 9227 and ATSM B-117, equivalent between them,

    which describes the chamber test dimensions, the fogging and the salt concentration (5% NaCl). On the other

    hand, there’s no indication about samples distribution neither results evaluation.

    The Salt Spray Chamber test evaluates the time (in hours) in which appears white and red corrosion. White corrosion

    indicates that Zinc oxidation has started. It will continue until Zinc is exhausted and iron oxidation starts

    when red corrosion appears. Red corrosion leads to the screw embrittlement and potential break may occur;

    therefore it’s very important to prevent its appearance. White corrosion is only relevant in


    important to mention that there’s no direct relationship between the

    hours resistance in Salt Spray Chamber to the corrosion resistance in

    real environment.

    The electrolytic coating consists in a metallic protective layer deposited on the screw surface by immersion in an

    aqueous solution. The process is the following: electric current is applied between the negative electrode with

    the chemical element for the screws protection (Zn, Ni, Cu, Sn) and the positive electrode in contact with the

    pieces to coat. The screw is coated by electrolytic exchange.

    The chemical element will depend on the coating performance desired: protection against oxidation, conductivity,


    For screws and other fixing elements, when high corrosion resistance is required, the chemical elements used

    are Zinc and its alloys Zn-Ni and Zn-Fe. The Zn layer and its alloys are not enough resistant and its required passivation,

    which will determine the final corrosion resistance and colour.

    RoHS and ELV European Directives restrict the use of certain hazardous substances. Initially it was only applied

    in Automotive and Electronic equipment, but now it is widely applied in other sectors.

    During the last years, new sealants have been developed for their application on electrolytic coatings (Zn, Zn-Ni

    and Zn-Fe) to improve the corrosion resistance.

    Cr VI is the last Chrome oxidation stage and it provides very high corrosion resistance. According to RoHS requirements,

    Cr III is substituting Cr VI, but it needs sealants to reach the previous corrosion resistance. The aesthetic

    appearance of Cr III coatings is not as good as the obtained with Cr VI coatings.

    Hydrogen Embrittlement

    The hydrogenation is the occlusion of hydrogen atoms in the metallic structure of the steel during electrolytic

    coating, causing microscopic cracks and loose of ductility. When we apply a high assembly torque or the

    screw is under high loads, the hydrogen atom can move through the screw core, creating internal tensions

    and causing break of the screw. This is known as hydrogen embrittlement and it could be detected as the

    screw head is broken some hours after the assembly. The risk of hydrogen embrittlement increases with the

    screw surface hardness.

    To avoid hydrogen embrittlement, pieces are baked. The Standard ISO 4042 recommends to proces the

    pieces between 200 and 230oC from 2 to 24h, depending on the type and geometry of the pieces, mechanical

    features and other processes applied.

    The hydrogen embrittlement affects to high hardness screws, so baking process is recommended for all screws

    with hardness over 320HV.

    The Standard ISO 4042 establishes that is not possible to guarantee the complete elimination of hydrogen

    embrittlement risk. If further reduced probability is desired it is needed alternative procedures.

    Baking process is applied in the following screws families:

    - TAPTITE II?, TAPTITE 2000?, FASTITE?2000?.


    - IBI-ZAS.

    - PLASTITE?.

    - Screws Class 10.9.

    - Screws Class 12.9.

    - Self-tapping screws under customer demand.

    Zinc-Aluminium Flake Coating.

    Organic coating made of Zinc and Aluminium flakes in solvent based dispersion. It can be applied by dipping

    or spraying, depending on the size of the parts and needs post curing with high temperature.

    For our product range, the organic coating is applied in a non-electrolytic dip-spin. It is recommended to apply

    a minimum of two layers to guarantee a uniform protective layer and the polymerisation takes place in the

    oven at 200oC. The final thickness of the coating is limited by the screw diameter, or, to be more exact, by

    the thread pitch. The Standard ISO 10683 specifies the maximum thickness for ISO machine threads according

    to their tolerance.

    We differentiate the Base Coat in grey colour and the Top Coat, which can be in many different colours,

    being grey, black and blue the most widely used. The application process is the same for both coats. The

    Base Coat provides real corrosion protection. Black, blue or other colours need from one to two grey layers,

    resulting in 4 to 5 layers application. The higher the number of layers is, the higher the probability to block

    the thread and the recess. The colour and high corrosion resistance application requirement can affect the

    thread performance.

    The organic coating accomplishes ELV and RoHS European Environmental Directives. It’s free of Cr VI and heavy

    metals like Cadmium, Lead and Mercury.

    For your convenience,

    we offer you the

    following packaging



    The screw reference and production

    batch is printed on the bag label,

    allowing a perfect traceability of

    the pieces.


    For big quantities and special production

    screws, the product is

    presented in bulks packing. The

    quantity per box and its dimensions

    will depend on the weight of the


    For your convenience,

    we offer you the

    following packaging



    The screw reference and production

    batch is printed on the bag label,

    allowing a perfect traceability of

    the pieces..


    For big quantities and special production

    screws, the product is

    presented in bulks packing. The

    quantity per box and its dimensions

    will depend on the weight of the


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